One practical scenario for the ID problem is when there is a network of internet-of-things (IoT) devices, such as sensors, that are controlled by a mobile phone. Suppose we want to save energy to increase the battery life of these sensors. One way to achieve this is to insert a physical unclonable function (PUF) [1]}, which can be any digital circuit with unique outputs, into each sensor such that a uniformly distributed secret key is assigned to each device. Each secret key is an identifier for the corresponding sensor, which can be shared with the mobile phone when secure transmission is possible or by using public key cryptography. When the mobile phone intends to control a particular sensor, this sensor's identifier and the command to this sensor are encoded and broadcast through a noisy wireless channel. All sensors first apply a binary hypothesis test to decide whether they are the targeted sensor. If this is not the case, they do not decode the command in order to save energy. Similarly, see [2]} for an application of the ID problem to digital watermarking.
